Mesoporous Titania Nanotubes: Their Preparation and Application as Electrode Materials for Rechargeable Lithium Batteries

Abstract

Mesoporous titania and titania nanotubes, with high surface-to-volume ratios, have recently been reported to demonstrate improved properties compared to colloids, films and other forms of titania in applications such as photocatalysts, [1,2] gas sensors, [3] photovoltaic cells [4][5][6] and rechargeable lithium batteries. [7][8][9][10] Therefore, particular attention has been paid to the preparation of titania nanotubes, or arrays of tubes, and many methods have been developed including the hydrothermal treatment of TiO 2 nanoparticles with alkali solution, [8][9][10][11][12][13] anodization of titanium foil, [14,15] deposition of sol-gels within templates, [16][17][18] hydrolysis of TiF 4 under acidic conditions, [19] sonication of titania particles in aqueous NaOH solution, [20] and surfactant-assisted templating methods. [21,22] Materials with mesoporous structures possess an extraordinarily high surface area. The synthesis of titania nanotubes, with mesoporous walls and hence high surface areas, will be invaluable for all applications employing the wide bandgap semiconductor. Therefore, there is a requirement for the development of a facile and reproducible way to prepare titania nanotubes with well-defined mesoporous wall structures. We have previously shown that one-dimensional mesoporous silica nanotubes and nanowires can be fabricated inside the pores of anodic aluminum oxide (AAO) membranes.[23] Recently, Chae et al. reported the preparation of titania nanofibres with wormhole-like mesoporous structure using AAO as a 'hard template'. [24] Even though mesoporous SiO 2 nanotubes and titania nanofibres have been prepared, the fabrications of TiO 2 nanotubes with well ordered mesopores are still a challenge because of the complexity of sol-gel chemistry. Herein, we report the preparation of titania nanotubes with mesoporous walls within AAO membranes and their application in a high rate rechargeable lithium battery. Well-aligned titania nanotube arrays were fabricated via a drying process utilizing supercritical CO 2 after the dissolution of the membranes. These mesoporous titania nanotubes, with a 3-dimensional (3D) network structure, were investigated as the electrode material of a rechargeable lithium battery. The structure of the mesoporous nanotubes was specifically designed to allow efficient transport of both lithium ions and electrons, which are necessary for a high rate rechargeable battery. The experimental results obtained proved that the mesoporous nanotube structure plays an important role in the efficiency of the high rate performance of the battery. Scanning electron microscope (SEM) images of the titania nanotubes annealed at 150°C are shown in Figure 1. Well-defined nanotubes are observed occupying most of the pores of the AAO. The size and uniformity of the nanotubes fabricated by this templating method are closely related to the pore size and quality of the alumina membranes employed.[17] Nanotubes prepared within a 0.2 lm Whatman AAO membrane have an outer diameter of approximately 200 nm...

Porous AgPd–Pd Composite Nanotubes as Highly Efficient Electrocatalysts for Lithium–Oxygen Batteries

“…Vigorous stirring was maintained throughout the entire process. The obtained composite was collected and aged in NH 3 •H 2 O for 1 d to remove the AgCl. Finally, the reaction mixture was diluted with water and acetone followed by centrifuging at 3000 rpm for 15 min.…”

“…This mixture was continuously refl uxed until its color became stable. Finally, the obtained composite (AgPd-1, AgPd-2, and AgPd-3 NTs) reaction mixture was collected and aged in NH 3 •H 2 O for 2 d to remove the AgCl. The obtained composites were further washed with water and acetone several times.…”

“…Therefore, the diffraction patterns can be indexed as mixed phase AgPd alloy Porous nanotubes (NTs) have become increasingly important nanomaterials in electronics, energy storage, catalysis, and fuel cell applications. [1][2][3][4][5][6][7] In contrast to the intact walls of conventional NTs, this structural feature will result in a much more adsorption effi ciency and abundant active catalytic sites, because molecules and electrolyte can enter into the hollow cavities of porous NTs via not only the two narrow ends but also holes along the tube wall. [ 3,[7][8][9] Especially in the fi eld of energy storage and conversion, these 1D porous nanostructures can also form a continuous conductive network and improve the adsorption of and immersion in electrolyte on the surfaces of electroactive materials in order to facilitate the electrode reaction kinetics for high energy density.…”

“…[1][2][3][4][5][6][7] In contrast to the intact walls of conventional NTs, this structural feature will result in a much more adsorption effi ciency and abundant active catalytic sites, because molecules and electrolyte can enter into the hollow cavities of porous NTs via not only the two narrow ends but also holes along the tube wall. [ 3,[7][8][9] Especially in the fi eld of energy storage and conversion, these 1D porous nanostructures can also form a continuous conductive network and improve the adsorption of and immersion in electrolyte on the surfaces of electroactive materials in order to facilitate the electrode reaction kinetics for high energy density. [10][11][12][13][14] This porous 1D structure will be even more promising for increasing the catalytic activities toward the two key processes in lithium oxygen battery, oxygen reduction reaction (ORR) (O 2 + 2Li + + 2e − → Li 2 O 2 ) and the oxygen evolution reaction (OER) (Li 2 O 2 → O 2 + 2Li + + 2e − ) by facilitating rapid O 2 diffusion and electrolyte accessibility, and providing more catalytic reaction sites for deposition of Li 2 O 2 .…”

The Development of Silicon Nanocomposite Materials for Li-Ion Secondary Batteries

“…nanometer-sized rutile TiO2 [52] mesoporous TiO2 nanotubes [53] mesoporous TiO2:RuO2 (nano) [54] Mesoporous polyaniline/anatase TiO2 [55] 160~50 162~100 214~20…”